As many of his fellow candidates flooded Iowa over the weekend to woo voters at the Ames Straw Poll, Mr. Perry headed to South Carolina announce he was seeking the nomination at the RedState Gathering, an annual convention of conservative bloggers.

“I came to South Carolina because I will not sit back and accept the path that America is on, because a great country requires a better direction, because a renewed nation needs a new president,” he said.

“With the support of my family and unwavering belief in the goodness of America, I declare to you today as a candidate for president of the United States.”

And with that, Mr. Perry, 61, whose spectral presence has lingered over the Republican primary contest — he was even the topic of a question at Thursday night’s Republican debate in Iowa — officially became a candidate for the Republican nomination.

Mr. Perry’s entrance into an already crowded field is expected to reconfigure the dynamics of the race, offering Republicans a fiscal and social conservative who not only appeals to the party’s base on social issues but also can challenge Mitt Romney, who is leading in many polls, on jobs and the economy.

His announcement reverberated 1,200 miles away in Iowa, where thousands of Republicans gathered to size up the party’s candidates, who delivered speeches and asked for support in the Ames Straw Poll. Though Mr. Perry’s name was not on the ballot, a group called Americans for Rick Perry urged people to list him as a write-in candidate.

In a sea of people wearing green shirts for Tim Pawlenty, orange shirts for Michele Bachmann and red shirts for Ron Paul, dozens of maroon shirts bearing Mr. Perry’s name stood out in the crowd. He is set to travel to Iowa on Sunday, where he intends to spend three days in the state introducing himself to voters who will open the nominating contest early next year.

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“He’s an attractive candidate,” said Tim Gibson, 59, of Clive, Iowa, who stood in line at the straw poll, waiting to cast his vote for Mr. Perry. “He brings leadership to the race. My top priority is winning the election, and I want to vote for someone who can win.”

Mr. Perry is the longest-serving governor of Texas, having been elected to three full terms and having held the position for more than 10 years. He is known as a fierce and skilled campaigner, as well as a prodigious fund-raiser. In past campaigns, he has eked out victories and also come from behind to win by large margins. He also possesses uncanny luck and the ability recognize and capitalize on it.

“He becomes immediately one of the top three candidates and he fills a vacuum, of someone who is a conservative, who has credibility and can speak to the fiscal conservative, anti-big-government and anti-Washington crowd, but he’s also a social conservative,” said Matthew Dowd, a former strategist for President George W. Bush. “At least in the short term, he is a major disruption in the race.”

Mr. Perry was heading to New Hampshire on Saturday evening and then to Iowa, but what he does in the coming weeks will be the real test of his candidacy, said Republicans who were waiting to see if he could withstand the scrutiny that comes with a presidential campaign.

“He either gets in and gets through the gantlet of the first month or so and consistently moves forward and wins the nomination, or he’s got this terrific flameout,” Mr. Dowd said. “There’s no middle ground.”

Mr. Romney has positioned himself as the candidate with real-world experience who can turn the economy around and create jobs, and Mr. Perry will compete with him on that front, having ushered in a decade of job growth in Texas. But not everyone is convinced that Mr. Perry’s tenure has been great for Texas.

“He’s cutting services in order to maintain really low tax rates, and so many of the jobs he’s created are these minimum-wage jobs, not these living-wage jobs,” said Representative Lloyd Doggett, Democrat of Texas. “I think he has, as they would say here in Texas, plenty of ’splaining to do about his positions.”

Mr. Perry, a fifth-generation Texan, grew up in a rural community in Paint Creek, on a tenant farm nestled in the West Texas plains, an area known as the “Big Empty.” Mr. Perry, an Eagle Scout, told Texas Monthly last year, “There were three things to do in Paint Creek: school, church and Boy Scouts.” His mother, he said, was a good seamstress who still made his underwear when he went off to college at Texas A&M University, from which he graduated in 1972 with a major in animal science.

Mr. Perry, a Methodist who regularly attends an evangelical megachurch near his home and hosted a large Nation in Crisis prayer rally this month in Houston, is a natural candidate to appeal to his party’s religious right, as well as to parts of its Tea Partycontingent.

In some ways, Mr. Perry embraced Tea Party ideals before the party itself was popular, winning re-election in 2010 — first by beating Senator Kay Bailey Hutchison in a primary challenge for governor, and then defeating Bill White, the former mayor of Houston — by positioning himself as an outsider, despite his two terms as governor. He pitted Texas against Washington, and prevailed.

Mr. Perry has walked a fine line on immigration, trying to balance his state’s business interests with calls for hard-line reform and border security, and that may not endear him with some Republicans, especially those aligned with the Tea Party.

In 2001, he signed his state’s version of the Dream Act, a bill that allowed children of illegal immigrants to attend state universities as long as they were working toward citizenship and had graduated from a Texas high school. Yet a decade later, he led the push for a “sanctuary city” bill that would have allowed the police to question people they picked up about their immigration status.

Mr. Perry is George W. Bush’s direct successor, and with his Texas twang and swagger, he can seem like a caricature of the former president. Voters trying to figure out what they think of Mr. Perry will invariably wrestle with their feelings about Mr. Bush, which, Republicans say, may become a potential liability if he makes it to the general election.

Though Mr. Perry is a disciplined campaigner, he has been known to get carried away when speaking, and sometimes finds himself trying to rein in his own statements. In 2009, he dabbled with secession.

“There really was considerable talk down here about all the talk of secession that bubbled up around his gubernatorial campaign,” Mr. Doggett said. “So that when he started talking about running for president, the question was: of which country?”

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